Solvent extraction of oil



Feb. 22, 1944. IR. E. MANLEY SOLVENT .EX'LRACL10N 0F OIL Y Filed July' 19, 1941 ambi, 3

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Patented Feb. 22, 1944 i soLvENT nx'rrtAorroN or om Robert E. Manley, Yonkers, N. Y., assigner, by mesne assignments, to .The Texas Company, `New York, N. Y., a corporation of Delaware A' Application Jniy 19, 1941, serial No.4o3,1oz i (ci. 19o- 13) Y 4 Claims.

This invention relates to the fractional separation of oil by extraction with a selective solvent and particularly to therfractlonal separation of hydrocarbon mixtures such as derived from petroleum which contain aromatic and non-aromatic hydrocarbons includingv aliphatic and alicyclicv 4 hydrocarbons.

The invention broadly contemplates extracting oil with a selective solvent which is substantially completely miscible with water at elevated temperature. The oil is extracted with the solvent to form extract and rafnate phases, each phase comprising a mixture of solvent and a portion of the oil. These phases are separated and separately ltreated with water in relatively, large amount andunder conditions such that a large proportion of the solvent is dissolved in the water to form a primary solution` of water and solvent, rich in solvent. The extract and ralnate phases from which the primary solutions have been removed are then separately treated'with an additional quantity of water so as to substantially completely remove the remaining solvent from the extract and ramnate oil respectively, thereby 1 forming secondary solutions of water and solvent.

The primary solutions are fractionally distilled t'o separate water from the solvent, forming a liquid fraction consisting essentially of solvent, and a distillate fraction comprising a mixture of solvent and water. The liquid fraction of recovered solvent is utilized for the extraction of fresh feed oil. I

The secondary solutions relatively lean in solvent are also fractionally distilled to form a distillate fraction in which the solvent is concentrated and a liquid fraction consisting essentially of water -substantially free from solvent.

The distillate fractions relatively'lean in solvent are accumulated and used for treating fresh extract and railinate phases for the production of further quantities of the primary solutions.

The water separatedfrom thefractional distillation of the secondary solutions may be discharged from the system or may be used as .the solventmedium in the subsequent extractionof the solvent free extract oil particularly for the purpose of effecting separation of aromatic constituents therefrom in concentrated form as will beV described in more detail.

The process of this invention is adapted to the treatment of relatively low boiling hydrocarbon mixtures such as naphtha or kerosene with selective solvents such as nitrobenzene, phenol, dichlorethyl ether, furfural or other furan cominvention. l5

pounds including furfuryl droiurfuryl alcohol, etc.

The invention is applicable tov the-treatment of hydrocarbon fractions such as crackedvnaphtha containing aromatic constituents s'uch as benzol, toluol and xylol for the purpose of separating these aromaticconstituents or mixtures thereof in a relatively concentrated form' from the feed. naphtha. j v

In order to describe the inventlonin more de- `tai1 reference will now be made tothe accompanying drawing comprising a iiow diagram illustrating one mode or practicing theprocessof the As shown in the drawing duced to the tower at a temperature of about 70 to 90 F.

A stream of solvent such as furfural is con-k ducted through a pipe I to the upper portion of the tower 24 and may be introduced thereto at a temperature of about. 90 to 100 F.

The tower is'is advantageously packed with a j vsuitable packing material such as Raschig rings and arranged to effect countercurrent flow between solvent and feed oil within the tower whereby the oil is subjected to countercurrent extraction with the solvent.

As a result of the extraction a rafnate phase comprising the insoluble hydrocarbon constituents including mainly paraiilns collects jin the upper portion of the tower 2 and is continuously discharged therefrom through a pipe 4.

Extract phase comprising constituents of the oil soluble in the solvent including aromatic andolenic constituents collects in the lower portion of the tower and is continuously discharged there-.

from through a pipe 5.

'I'he extraction in the tower I is advantageously carried out under substantially atmospheric pres; sure or under a pressure sumcient to maintain liquid phaseqconditlons within the tower. The actual pressure employed will .depend upon the temperatures prevailing within the extraction tower.

The raillnate phase being discharged from lthe n top of the tower and containing about 10-15% by volume of solvent .is pumped under pressure through a heater 6 wherein it is heated to a temperature of about 300 F.. been rst commingled with a quantity of water obtained through a pipe 1 from a source which' will be described later. 'I'he rafllnate phase and water are alcohol and' tetrahya charge voil'suchas cracked naphtha is conducted from a sourcenot lshown through a pipe I to the lower portion afan. extractiontower 2. The feed oil may be-intro-ffy advantageously mixed in the proportion of about 0.5 to 1.0 volume oi water to one volume of raffinate phase.

The heated mixture is conducted from the heater to a separator 8 maintained at about 300 F. and under'pressure sumcient to maintain the mixture substantially in the liquid phase so that the mixture separates into liquid layers. The upper layer will comprise raffinate oil still retaining a small amount of solvent, i. e.. about 0.5% or less, while the bottom layer comprises water containing the bulk of the solvent. The bottom layer is continuously discharged from the bottom of the separator as a primary solution of solvent in water.

The railinate oil retaining the small amount of solvent is continuously withdrawn and conducted through a pipe 9 to the lower portion of an extractor I wherein it is subjected to countercurrent extraction with hot water, continuously introduced to the upper portion of the extractorV through a pipe II. 'I'he water is advantageously introducedfat a temperature of about 300 F. and in the proportion of about 1 to 2 volumes of water per volume of entering raflinate oil so that the extraction in the extractor I0 is effected at substantially this same temperature thereby dissolving the remaining solvent substantially completely from the raffnate oil.

The ra'inate oil substantially free from solvent is discharged through a pipe I2, while the water containing the extracted solvent is discharged from the bottom of the extractor as secondary solution through a pipe I3.

'I'he secondary solution is conducted through the pipe I3 to a receiving tank I4 and from there is charged to the lower portion o! a fractionator I5. 'I'he fractionator I5 serves as a distillingl column having provision for the introduction of steam to the lower portion thereof. The bottom of the fractionator is maintained at a temperature about 215 to 225 F. while theA top of the fractionator is maintained at a temperature of about 212 F., the pressure being maintained at substantially atmospheric.

Under these conditions the solvent is stripped from the bulk of the water, the water being discharged from the bottom of the fractionator through a pipe I6. This water is substantially free from solvent or at least contains only a trace or relatively small amount of solvent.

The distillate discharged from the top of the fractionator I5 comprises a mixture of water and solvent containing about 35% solvent.

This distillate is conducted through a pipe I1 and a condenser I8 from which the resulting condensate is conducted to a separator I8.

The mixture of waterI and solvent at a temperature of about 160 F. separates into layers within the separator I9, the upper layer comprises water relatively lean in solvent (containing, for example. about 13% by weight furfural) and it is continuously withdrawn therefrom through a pipe 20 which communicates with the Vpreviously mentioned pipe 1 and Athrough which this water saturated with solvent is introducedto the ramnate phase passing through the 320 to 330 F. and from there discharged into the lower portion of a, fractionator 23.

In the fractionator 23 the mixture of water and solvent is subjected to fractional distillation to strip the water from the solvent forming a liquid fraction consisting of recovered solvent substantially free from water which is discharged through a pipe 24 to a tank 25. The distillate fraction comprising water containing some solvent, for example, about 45% solvent, is discharged from the top of the fractionator through a pipe 25 to the previously mentioned condenser Il.

The fractionator 23 is advantageously operated under substantially atmospheric pressure with a temperature of about 325 F. at the bottom of the tower and a temperature in the range 220 to 260 F. at the top of the tower. The desired temperature conditions are maintained by the introduction of a suitable reflux liquid to the upper portion of the tower. This reflux liquid advantageously comprises a portion of the relatively cool feed to the heater 22.

The recovered solvent collecting in the tank 25 is conducted through a pipe 21 for return to the upper portion of the extraction tower 2.

The extract phase discharged from the ex .:rator 8.

The resulting bottom layer comprising water rich in solvent and designated as primary solution is conducted through pipe 33 to the previously mentioned separator I9.

The upper layer comprising extract oil relatively free from solvent containing, for example, about 0.5% solvent) is conducted through a pipe 34 to the lower portion of an extractor 35 wherein it is likewise extracted withhct water at a temperature of about 300 F.

'Ihe resulting secondary solution comprising water relatively lean in solvent is drawn off through a pipe 36 and discharged in the previously mentioned tank I 4.

The extract oil now free or substantially free from solvent is removed from the top of the exractor 35 through a pipe 31 to a receiving tank As previously indicated, where the feed oil comprises cracked naphtha this extract oil will usually comprise aromatic hydrocarbons including toluene and in addition will contain oleilnic hydrocarbons.

Where it is desired to separate the toluene or the extract oil is subjected to a subsequent treatment which may involve extraction with a suitable solvent under conditions adapted to selectively separate the toluene. 'I'his may be accomplished, for example, by extraction with water at elevated temperature and pressure.

In such. case the extract oil is pumped through a heater 39 wherein it is heated to a temperature of about 400 to 600 F. The heated mixture is introduced to the lower portion of a countercurrent extraction tower 40 similar to the previously described extraction tower 2.

. with some water.

,A stream of water is conducted from atank 4I through a heater 42 wherein it is heated to a temperature in the range about 400 to 600 F. l

and thereafter introduced to the upper portion 'of the extraction tower 40 in the proportion of about 1 to 12 volumes or moreY of Awater to 1 volume of hydrocarbon feed.

The extraction tower 40 is maintained under v a pressure which may range from about 1000 to 'a 5000 pounds per square inch gauge,'or sufficient to maintain substantially liquid phase conditions within the extraction tower 40. 4

The water/and extract oil are subjected to countercurrent contact within the extraction tower 40. As a result a water "phase collects in the bottom of the extraction tower lcomprising aromatic hydrocarbons'` dissolved in the bulk of the water while a hydrocarbon'phase collects in the upper portion of the extraction tower and comprises non-aromatic hydrocarbons 'mixed The hydrocarbon phase is continuously discharged from the top of the tower through a pipe 43 and cooler 44 to a separating lvessel 45. The mixture is advantageously cooled to a temperature of about 70 F. as a result of which the layers, respectively, in the separator 45. The water layer can be continuously discharged from hydrocarbonfraction is continuously discharged from the top of the separator45.

Likewise, the water phase is continuously withd drawn from the bottom of the extraction tower 40 through a pipe 46, cooler 41 and from there discharged into a-separator 48. The water phase is advantageously cooled to'a temperature of about 70 to 150 F. so Athat separation occurs within the separator 48 into layers or phases due to the relative insolubility of the aromatic hydroature. The Varomatic hydrocarbons Aare discharged through a pipe 49 while the water layer is discharged through a pipe 50, and returned all or in part to the previously mentioned tank 4I.

'I'he extraction in the extraction tower 40 may be effected with water .containing substantial amounts of .fu'rfural or dissolved'selective solvent'. For example, the extraction medium may comprise water containing about 8 to 15% by weight of furfural. Therefore, instead of using water drawn off from the pipe I6 as the extraction medium a portion of the water solvent mixture discharged from pipe 20 nay be used since as already mentioned, the mixture flowing through pipe 20 from the separator I9 comprises water containing about 13% by weight lof furfural. `A portion of this stream may beY diverted inlet of the heater 42 wherein it is heated prior to introduction to the extraction tower 40.

While specific operating conditions havebeen described in connection with the flow diagram it is contemplated that these conditions may be varied depending upon'the naturev of the oil undergoing treatment and the particularselective solvent employed. It is also contemplated that the specific method of flow may be modified, as for example, to provide additional stages of extraction and/or fractionation.

kerosene and the like or fractions thereof. For

The water advantaf geously comprises that discharged from the bottomof the fractionator I5.

mixture separates into water and hydrocarbonl carbons in the vsolvent at the reduced temper-v asians example, where the recovery of aromatic hydrocarbons such as toluene from cracked naphtha is of primary interest, selected feeds rich in aromatic hydrocarbons may be used. Thus, the feed may advantageously comprise a naphtha fraction consisting essentially of hydrocarbons having 5 to 7 carbon atoms permolecule.

. While application ofthe process to the treat-A ment of mineral oils has been specifically described, nevertheless it is contemplated that the process may be applied to the treatmentof other oils including fatty oils and fatty acids, such as are used in the preparation of foods, soaps,l

paints, varnishes and enamels. Examples of such other oils include linseed oil, tung oil, soybean oil, cottons'eed oil, etc. Numerous other oil l substances may be mentioned including fatty acids, fatty acid mixtures and mixtures of fats and foils as well as rosin and rosin oils.

Obviously many modifications and variations of the invention, as hereinbeforeI set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be 'imposed as are indicated in the appended claims. Y

'I claim:

1. In a continuous process for extracting aro- Y matic hydrocarbons from a hydrocarbon mixture the bottom of the separator and returned all or in part to the tank 4I while the non-aromatic containing aromatic and non-aromatic constituents including paraiiins and naphthenes which comprises extracting the hydrocarbon feed with a selective solvent substantially completely milscible with water in all proportions at elevated temperatures and having the essential selective solvent action of furfural as between parans and non-paramns to form a rafiinatephase comprising parafiinsand an extract phase comprising through a pipe 5l and thereby conducted to the non-paraiiins dissolved in the bulk of the solvent, separating the resulting phases, subjecting the .extract phase to the extractive action of water in suiiicient amount to substantially dissolve the I solvent thereby forming a primary solution ofv water and solvent, removing the primary solution, separately subjecting the remaining extract. retaining some solvent, to further extraction with water at elevated temperature to extract remaining solvent therefrom and thereby form a secondary solutionof water and solvent, and a secondary extract of extract hydrocarbons, distilling said secondary solution with the aid of steam to form a liquid fraction consisting essentially of water and a distillate fraction of enriched solvent content, passing said distillate to a separating zone Jmaintainedat a temperature such that separation into phases occurs, passing said primary solution to the separating zone for phase separation therein in the presence of the said distillate, withdrawing from the separating zone a mixture comprising water lean in solvent, recycling the so Withdrawn mixture'for mixing with fresh extract phase, separately withdrawing from the separating zone a mixture comprising water rich in solvent, subjecting this -solvent rich lmixture to distillation toform a v solvent and water, passing said second distillate to the separator, passing said secondary extract hydrocarbons to an extraction zone, also passing to said extraction zone the aforesaid liquid fraction consisting essentially of water, subjecting the extract hydrocarbons and water therein -to a temperature in the range about 400 to 600 F. and while under elevated pressure sufficient to maintain substantially liquid phase conditions and such that aromatic hydrocarbons are dissolved in the water, removing the water and dissolved aromatica andrecovering the aromatics from the'removed water.

2. A continuous process for effecting fractional separation of oil by extracting the oil with a substantially water free selective solvent and which solvent is completely miscible in water in all proportions at elevated temperatures comprising subjecting the oil to extraction with the solvent, forming an extract phase comprising a portion of the solvent and constituents of the oil dissolved herein and a raiiinate phase comprising another portion of the solvent and constituents of the oil insoluble in the solvent, separating said phases, separately treating said phases with water at elevated temperature and in sumcient amount to substantially dissolve the solvent therebyforming primary solutions of water and solvent. yremoving Aand commingling said primary solutions, separately subjecting the remaining ext'act and railinate phases each containing some solvent to extraction with water at elevated temperature to extract remaining solvent therefrom and thereby fonn secondary solutions of water and solvent, commingling said secondary solutions,- distilling the commingled secondary solutions with the aid of steam to form a liquid fraction consisting essentially of water and a distillate fraction of enriched solvent content, passing said distillate to a separating zone maintained at a temperature such that phase separation occurs, passing said commingled primary solutions to the separating zone for phase separation therein in the presence of said distillate, withdrawing from the separating zone a mixture of water lean in solvent, recycling the so withdrawn water for mixing with fresh extract and raiiinate phases, separately withdrawing from said separating zone a mixture comprising water rich in solvent, subjecting this Water-rich mixture to distillation to form a second lquid fraction consisting essentially of dry solvent and a second distillate fraction comprising solvent and water, recycling the second liquid fraction for mixing with fresh feed oil, and commingling said second distillate fraction with the aforesaid distillate of enriched solvent content.

3. A continuous process for effecting fractional separation of oil by extracting the oil with a substantially water-free selective solvent and which solvent is completely miscible in water inV al1 proportions at elevated temperatures compricing subjecting the oil ilo extraction with the solvent, forming an extract phase comprising a crton of the solvent and constituents of the cil dissolved therein and a railinate phase compricing another portion of the solvent and constituents of the oil insoluble in the solvent, separn ting said phases, treating the extract phase with water at elevated temperature and in suicient amount to substantially dissolve the solvent, thereby forming a primary solution of water and solvent, removing said primary solution, subjecting the remaining extract phase containing some solvent to extraction with water at elevated temperature to extract remaining solvent l e and thereby form a secondary solution of wate and solvent. distilling the secondary solution wi the aid of steam to form a liquid fraction con sisting essentially of water and a distillate frac tion of enriched solvent content, passing distillate to a separating zone maintained at temperature' such that phase separation occurs passing said primary solution to the separa zone for .phase separation therein in the presen of said distillate, withdrawing from the separa ing zone a mixture of'water lean in solven recycling the so withdrawn water for I with fresh extract phase. separately withdra 1 from said separating zone a mixture comp M water rich in solvent, subjecting this water ri mixture to 'distillation to fonn a second liqui fraction consisting essentially of dry solvent a second distillate fraction comprising solven and water,`recycling the second liquid l l for mixing with` fresh feed oil and comming z said second distillate fraction with the afo distillate of enriched solvent content.

4. A continuous process for effecting fracti separation of oil by extractingthe oil with substantially water-free selective solvent which solvent is completely miscible in water i all proportions at elevated temperatures com prising subjecting the oil to extraction with solvent, forming an extract phase comprising portion of the solvent and constituents of m cil dissolved therein and a raiiinate phase com prising another portion of the solvent and con stituents f the oil insoluble in the solvent, sepa rating said phases, treating the railinate p with water at elevated temperature and in suiii cient amount to substantially dissolve the solvent thereby forming a primary solution of water an solvent, removing said primary solution subjec the remaining raflinate phase containing som solvent to extraction with water at elevated tem perature to extract remaining solvent theref mand thereby form a secondary solution of wa and solvent, distilling 'the secondary solu l with the aid of steam to form a liquid fracti consisting essentially of water and a disidlla fraction of enriched solvent content, passing sai distillate to a separating zone maintained at temperature such that phase separation occurs passing said primary solution to the separa zone for phase separation therein in the presen of said distincte, withdawing from the separa ing zone a mixture of water lean in solvent, re cycling the so withdrawn water for mixing wi fresh railinate phase, separately withdra .y

from saidseparating zone a mixture comp n water rich in solvent subjecting this water ri mixture to distillation to form a second liquid fraction consisting essentially of dry solvent and a second distillate fraction comprising solven and water. recycling the second liquid fraction for mixing with fresh feed oil and commingling said second distillate fraction-with the aforesaid distillate oi enriched solvent content.

ROBERT E. MANLEY. 

